The purpose of this study is to evaluate the long-term antibody persistence from 6, 7, 8, 9 to 10 years post-administration of MenACWY-TT conjugate vaccine as compared to Mencevax ACWY when given to healthy subjects 11 to 55 years of age. In addition, the safety and immunogenicity of a booster dose of MenACWY-TT vaccine administered to all eligible subjects 10 years after the primary vaccination will be evaluated.